1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to controlling a transmission rate, and more particularly, to a method of controlling a transmission rate based on a transmission protocol which supports multi-homing, and to a communication device using the same.
2. Description of the Related Art
Stream Control Transmission Protocol (SCTP) is a next-generation transmission protocol following Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). Similar to the TCP, the SCTP provides connection-oriented, reliable data transmission. In particular, the error and flow control of the SCTP is the same as that of the TCP.
One of the main differences between the SCTP and the TCP is that multi-homing and multi-streaming are supported. For example, multi-homing allows multiple paths to be used for packet transmission between communication devices. In this case, if a problem occurs in one path, another path can be used, and thus multi-homing provides seamless packet transmission between the communication devices.
A path for packet transmission is changed, for example, upon handover of the communication device. In the related art, when the path is changed, as shown in FIG. 1, like an initial process of a session, a congestion window is set to a default value (10), regardless of the communication environment of a new path. Then, the communication device controls a transmission rate through a slow-start process (20) and a congestion avoidance process (30), and thus the data transmission amount during the handover is drastically reduced and then is gradually increased. With respect to the above, service quality is greatly influenced according to kinds of service to be used by the communication device. For example, when the communication device is executing a voice call service using Voice over Internet Protocol (VoIP), a call delay may be long. Further, when the communication device is using a streaming service, video dropping and blocking may occur.
Accordingly, a technique which can keep the transmission rate uniform even though the path for packet transmission is changed when packet transmission is based on multi-homing is demanded.
Korean Unexamined Patent Publication No. 2001-0043592, entitled “Soft Handoff in Cellular Mobile Communication Network”, discloses a soft handoff technique in a cellular mobile communication network which includes signal measurement values for base transceiver stations involved in a handoff operation into one or more uplink signals and causes the individual signal measurement values to be used to represent performance of communication channels between the associated base transceiver stations and a mobile station. According to the technique described in Patent Document 1, the communication device can select a channel having excellent performance among a plurality of channels. However, Korean Unexamined Patent Publication No. 2001-0043592 does not describe a technique for allowing the communication device to perform the active control of the transmission rate.